In this paper, we investigate the detectability problem in discrete event systems. We assume that we do not know initially which state the system is in. The problem is to determine the current and subsequent states of the system based on a sequence of observation. The observation includes partial event observation and/or partial state observation, which leads to four possible cases. We further define four types of detectabilities: strong detectability, (weak) detectability, strong periodic detectability, and (weak) periodic detectability. We derive necessary and sufficient conditions for these detectabilities. These conditions can be checked by constructing an observer, which models the estimation of states under different observations. The theory developed in this paper can be used in feedback control and diagnosis. If the system is detectable, then the observer can be used as a diagnoser to diagnose the failure states of the system.

Interorganizational cooperation is more and more organized by the paradigm of services. The service-oriented architecture (SOA) provides a general framework for service interaction. It describes three roles, service provider, service requester, and service broker, together with the three operations publish, find, and bind. We provide

In this paper we formulate asynchronous diagnosis by means of hidden state history reconstruction, from alarm observations. We follow a so-called true concurrency approach, in which no global state and no global time is available. Instead, we use only local states in combination with a partial order model of time, in which local events are ordered if they are either generated on the same site, or related via some causality relation. Our basic mathematical tool is that of net unfoldings originating from the Petri net research area. This study was motivated by the problem of event correlation in telecommunications network management.

We consider a generalized form of the conventional decentralized control architecture for discrete-event systems where the control actions of a set of supervisors can be "fused" using both union and intersection of enabled events. Namely, the supervisors agree a priori on choosing "fusion by union" for certain controllable events and "fusion by intersection" for certain other controllable events. We show that under this architecture, a larger class of languages can be achieved than before since a relaxed version of the notion of co-observability appears in the necessary and sufficient conditions for the existence of supervisors. The computational complexity ofverifying these new conditions is studied. A method of partitioning the controllable events between "fusion by union" and "fusion by intersection" is presented. The algebraic properties of co-observability in the context of this architecture are presented. We show that appropriate combinations of fusion rules with corresponding decoupled local decision rules guarantee the safety of the closed-loop behavior with respect to a given specification that is not co-observable. We characterize an "optimal" combination of fusion rules among those combinations guaranteeing the safety of the closed-loop behavior. In addition, a simple supervisor synthesis technique generating the in mal prefix-closed controllable and co-observable superlanguage is presented.

Distributed discrete-event systems, in which agents (or local sites) are required to communicate in order to perform some speci ed monitoring and control tasks, are considered. Each agentis modeled as a nite-state machine that must be able to distinguish between its states to perform some required task. To help it disambiguate states, an agent uses a combination of direct observation (obtained from sensor readings available to that agent) and communicated information (obtained from sensor readings available to another agent). Since communication may be costly, a strategy to minimize communication between sites is developed. The complexity of the solution re ects the interdependence of the agents' communication protocols. That is, the decision to communicate the occurrence of an event relies on which event sequences are indistinguishable to an agent, which, in turn, is a result of what has already been communicated to that agent.

We introduce a new notion of decentralized observability for discrete-event systems, which we call joint observability. We prove that checking joint observability of a regular language w.r.t. one observer is decidable, whereas for two (or more) observers the problem becomes undecidable. Based on this result, we show that a related decentralized control problem is also undecidable. We finally provide an extensive study relating our work to existing work in the literature.

Abstract. Recently, we introduced the concept of an operating guideline of a service as a structure that characterizes all its properly interacting partner services. The hitherto considered correctness criterion is deadlock freedom of the composition of both services. In practice, there are intended and unintended deadlock-freely interacting partners of a service. In this paper, we provide a formal approach to express intended and unintended behavior as behavioral constraints. With such a constraint, unintended partners can be “filtered ” yielding a customized operating guideline. Customized operating guidelines can be applied to validate a service and for service discovery. Key words: Business process modeling and analysis, Formal models in business

Supervisory control problem of discrete event systems with temporal logic specifications is studied in this paper. The full branching time logic{CTL* is used for expressing specifications of discrete event systems. The control problem of CTL* is reduced to the decision problem of CTL*. A small model theorem for the control of CTL* is obtained. It is shown that the control problem of CTL* (resp., CTL) is complete for deterministic double (resp., single) exponential time. A sound and complete supervisor synthesis algorithm for the control of CTL* is provided. Special cases of the control of computation tree logic (CTL) and linear-time temporal logic (LTL) are also studied. Finally, a simple example is given for illustration. The contribution of the paper is summarized as follows: (i) For the first time a sound and complete supervisory synthesis algorithm for CTL* specifications has been obtained; (ii) Usage of temporal logic makes the specification specifying process easier and user-friendly since natural language specifications can be easily translated to temporal logic specifications (when compared to formal language/automata-based specifications) and at the same time there is no increase in the computational complexity (when compared to that of formal language/automata-based specifications); (iii) CTL* temporal logic allows the control constraints on the sequences of states which can be also captured by a regular -language or !-language, as well as on the more general branching structures of states which can not be captured by a regular -language or !-language.

The problem of verifying the properties of diagnosability and I-diagnosability is considered. We present new polynomial-time algorithms for deciding diagnosability and I-diagnosability. These algorithms are based on the construction of a nondeterministic automaton called a verifier.

This paper deals with diagnosing dynamical systems represented by a discrete-event model and more precisely represented in an automata formalism. It shows how model-checking techniques which have been designed for efficiently testing complex real-time systems can be exploited for diagnostic task. This work originates from an application in the monitoring of agricultural plots which has been implemented by using these model-checking techniques.